With shock waves and ultrasound therapy systems, in particular lithotripters, it is necessary to position the focus of the therapy source to the patient in a defined manner. For this, it is known to lay the patient onto a movable patient rest which can be moved in three spatial coordinates relative to the therapy source. Thereby, it is known to carry out the positioning amid the aid of X-ray pictures or ultrasound pictures. Such a device is known for example from EP 2 308 398 A1.
From this document, it is already known to arrange positioning keys or buttons on the picture representation of the ultrasound or X-ray picture, and these permit the displacement of the patient such that the therapy focus is moved in the picture. The disadvantage with these arrangements is the fact that it often occurs that the physician loses sight of the point to be treated, for example a stone, from the recorded ultrasound picture, on account of the displacement movement along the three spatial coordinates and being necessary for positioning. This renders the positioning quite difficult.